1. Field of the Invention
This invention relates to a photosensitive composition which is useful for a fine working in the manufacture of a semiconductor element and the like.
2. Description of the Related Art
In the manufacture of electronic parts such as an LSI, a fine working technique utilizing a photo-lithography has been employed. In this fine working technique, a resist material is commonly employed. In particular, in order to cope with a recent trend to further increase the integration density of electronic parts, the formation of extremely fine patterns of resist film is now required in the manufacture of electronic parts.
Under such a circumstance, attempts to use a light of shorter wavelength as a light source in the formation of resist film pattern is now progressing. Namely, methods for forming an ultra-fine resist pattern through the use of KrF excimer laser beam (248 nm in wavelength) or through the irradiation of an ionizing radiation such an electron beam or X-rays have been developed. At the same time, various kinds of resist material which are highly sensitive to the aforementioned light sources have been reported.
For example, Japanese Patent Unexamined Publication S/63-27829 discloses a chemically amplified resist consisting of a composition comprising an alkali-soluble resin, a solubility-inhibiting agent and a photo-acid-generating agent. According to a chemically amplified resist of this kind, the solubility of a resist to an alkali-developing agent is inhibited by the solubility-inhibiting agent at the non-exposure portion, while an acid is generated from the photo-acid-generating agent at the exposure portion so as to decompose the solubility-inhibiting agent in the following baking step after the light exposure. As a result, the portion of the resist that has been exposed to light is made soluble by an alkali developing agent. In this case, even if the amount of the acid generated from the photo-acid-generating agent is very little in the chemically amplified resist, it is still capable of decomposing a large amount of the solubility-inhibiting agent, so that an ultra-fine pattern can be generally obtained with high sensitivity.
Meanwhile, with the advancement of high integration density as seen in an LSI, the formation of a pattern having a line width in the order of sub-half micron has been made possible by the latest fine working technique. This trend of forming a finer pattern is expected to be more accelerated in future. Therefore, the utilization of a light of shorter wavelength as a light source in photolithography is now studied, i.e. the utilization of ArF excimer laser beam (193 nm in wavelength) or the quintuple harmonic beam of YAG laser (218 nm in wavelength) for the formation of a fine resist pattern is tried at present. Moreover, a study of an exposure with F.sub.2 excimer laser beam is also now attempted.
However, since the aforementioned conventional chemically amplified resist generally includes as a photo-acid-generating agent an aryl onium salt having a benzene ring, such a chemically amplified resist tends to exhibit a large light absorption by the benzene ring thereof when a light of short wavelength as mentioned above is employed. Therefore, it is impossible, because of this large light absorption, to allow the exposure light to reach deep enough to an interface between the resist film and the substrate during the light exposure in the formation of a resist pattern, thus making it very difficult to form a fine pattern which is excellent in shape and in precision.
As explained above, although the conventional chemically amplified resist may be useful for forming an ultra-fine pattern with high sensitivity when the g-line or i-line (each being an emission line from a low pressure mercury lamp) or KrF excimer laser beam (248 nm in wavelength) is employed as a light source, the conventional chemically amplified resist is still unsuited for forming a resist pattern of excellent resolution when ArF excimer laser beam is employed as a light source, because of its poor transparency to ArF excimer laser beam light.